Method and apparatus for mapping and de-mapping in an optical transport network

ABSTRACT

Methods and apparatuses for mapping processing and de-mapping processing in an optical transport network are provided. A Low Order Optical Channel Data Unit (LO ODU) signal is mapped into a payload area of an Optical Channel Data Tributary (ODTU) signal in units of M bytes. M is equal to the number of time slots of a High Order Optical Channel Payload Unit (HO OPU) that are to be occupied by the ODTU signal, and M is an integer larger than 1. Overhead information is encapsulated to an overhead area of the ODTU signal. Thereafter, the ODTU signal is multiplexed into the HO OPU. According to the application, an efficient and universal mode for mapping the LO ODU to the HO OPU is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/691,273, filed on Nov. 21, 2019, now U.S. Pat.No. 11,063,686, which is a continuation of U.S. patent application Ser.No. 15/859,092, filed on Dec. 29, 2017, no U.S. Pat. No. 10,505,662,which is a continuation of U.S. patent application Ser. No. 15/073,439,filed on Mar. 17, 2016, now U.S. Pat. No. 9,882,672, which is acontinuation of U.S. patent application Ser. No. 14/566,478, filed onDec. 10, 2014, now U.S. Pat. No. 9,312,982, which is a continuationapplication of U.S. patent application Ser. No. 12/712,675, filed onFeb. 25, 2010, now U.S. Pat. No. 8,948,205, which claims the benefit ofpriority to Chinese Patent Application No. 200910106028.2, filed on Mar.9, 2009. All of the afore-mentioned patent applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present invention relate to the field ofcommunication technologies, and particularly, to a mapping technique inan optical transport network.

BACKGROUND

With the quick development of communication technology, the OpticalTransport Network (OTN) with advantages of flexible scheduling andmanagement of large capacity services is increasingly becoming a majortechnology of the backbone transport network. In the OTN, the clientdata is encapsulated into an Optical Channel Payload Unit (OPU), someoverhead (OH) is added to the OPU to constitute an Optical Channel DataUnit (ODU), some OH and Forward Error Correction (FEC) is added into theODU to constitute an Optical Channel Transport Unit (OTU), and isfinally transmitted in the form of OTU.

With the rapid development of data service, more and more clients adoptEthernet technology as the physical interface at the client side. It isforeseeable that in the coming years, the Ethernet service will keep acontinuous high-speed growth. However, the current OTN technology isdesigned based on speech service such as synchronous digital hierarchy(SDH), and cannot well support the development trend of data servicelike Ethernet, thus studies are gradually carried out on the nextgeneration of OTN network (NG OTN). The NG OTN is required to not onlymeet the requirements of services newly appear, but also bear thecurrent OTN. Thus how to map a Lower Order Optical Channel Data Unit (LOODU) to a Higher Order Optical Channel Data Unit (HO ODU) is a focusbeing discussed in the industry. The LO ODU may be ODUk (k=0, 1, 2, 2e,3, 3e) existing in the current OTN, and herein represented as LO ODUk(k=0, 1, 2, 2e, 3, 3e); the HO ODU may be regarded as a datatransmission unit of higher rate, which belongs to the category of theNG OTN and is used for bearing the LO ODU, the corresponding OPU isrepresented as HO OPUk (k=1, 2, 3, 3e, 4).

The conventional technical solution maps the standard ODUj (j=1, 2) (for20 ppm bit tolerance) into the OPUk (k=2, 3) in an asynchronous manner.The asynchronous method maps the ODUj signal into the OPUk through anadjustment policy of −1/0/+1/+2. With the asynchronous manner, a maximumbit error tolerance between ODU1 and OPU2 is −113 to +83 ppm, a maximumbit error tolerance between ODU1 and OPU3 is −96 to +101 ppm, and amaximum bit error tolerance between ODU2 and OPU3 is −95 to +101 ppm.

However, the conventional method is not suitable for mapping the LO ODUinto the HO ODU, e.g. for ODU2 e (100 ppm bit tolerance), etc. ODUflexof higher bit tolerance may occur, and the adjustment policy of−1/0/+1/+2 does not meet the requirement for mapping the LO ODU into theHO ODU.

SUMMARY

The embodiments of the present invention provide method and apparatusfor mapping and de-mapping in an Optical Transport Network (OTN), so asto map a Low Order Optical Channel Data Unit (LO ODU) signal into a HighOrder Optical Channel Payload Unit (HO ODU) universally and efficiently.

The embodiments of the present invention provide a mapping method in anOTN.

First, a Low Order Optical Channel Data Unit (LO ODU) signal is mappedinto a payload area of an Optical Channel Data Tributary Unit (ODTU)signal in units of M bytes, wherein M is equal to the number of timeslots of a High Order Optical Channel Payload Unit (HO OPU) that are tobe occupied by the ODTU signal, and M is an integer larger than 1.

And, overhead information is encapsulated to an overhead area of theODTU signal.

Finally, the ODTU signal is multiplexed into the HO OPU.

The embodiment of the present invention also provides an apparatus forprocessing data in an OTN.

The apparatus comprises a processor and a computer readable mediumhaving a plurality of computer executable instructions stored thereon.The instructions when executed by the processor, would cause theprocessor to perform the steps of above mapping method.

The embodiments of the present invention also provide a de-mappingmethod in an OTN.

In the de-mapping method, first parse a HO OPU to obtain an ODTU signal.

Then, de-map in units of M bytes to obtain a Low Order Optical ChannelData Unit (LO ODU) signal from a payload area of the ODTU signal,wherein M is equal to the number of time slots of the HO OPU that areoccupied by the ODTU, and M is an integer larger than 1.

The embodiments of the present invention further provide a de-mappingapparatus in an OTN.

The de-mapping apparatus comprises a processor and a computer readablemedium having a plurality of computer executable instructions storedthereon. The instructions when executed by the processor, would causethe processor to perform the steps of above de-mapping method.

The embodiments of the present invention further provide a mappingapparatus in an OTN. The mapping apparatus comprises a mapping unit, aencapsulating unit and a multiplexing unit. The mapping unit isconfigured to map a Low Order Optical Channel Data Unit (LO ODU) signalinto a payload area of an Optical Channel Data Tributary Unit (ODTU)signal in units of M bytes, wherein M is equal to the number of timeslots of a High Order Optical Channel Payload Unit (HO OPU) that are tobe occupied by the ODTU signal, and M is an integer larger than 1. Theencapsulating unit is configured to encapsulate overhead information toan overhead area of the ODTU signal. The multiplexing unit is configuredto multiplexing the ODTU signal into the HO OPU.

The embodiments of the present invention further provide a de-mappingapparatus in an OTN. The de-mapping apparatus comprises a paring unit, ade-mapping unit. The parsing unit is configured to parse a High OrderOptical Channel Payload Unit (HO OPU) to obtain an Optical Channel DataTributary Unit (ODTU) signal. The de-mapping unit is configured tode-map in units of M bytes to obtain a Low Order Optical Channel DataUnit (LO ODU) signal from a payload area of the ODTU signal, wherein Mis equal to the number of time slots of the HO OPU that are occupied bythe ODTU, and M is an integer larger than 1.

In the above embodiments, optionally, the encapsulated overheadinformation may comprises information indicating the number of M-bytedata units of the LO ODU signal that are mapped during a multi-frameperiod

According to at least some of the embodiments of the present invention ahigh-efficient and universal mode for mapping LO ODU to HO OPU isachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the technical solutions of the embodiments of thepresent invention more clearly, the drawings needed for describing theembodiments are introduced briefly as follows. It is apparent that thefollowing drawings are just some embodiments of the present invention,and a person skilled in the art can obtain other drawings based on thesedrawings without paying a creative effort.

FIG. 1 is a flowchart of a mapping method in an OTN according to anembodiment of the present invention;

FIG. 2 is a structural schematic view illustrating dividing an HO OPUinto eight 1.25 G time slots according to an embodiment of the presentinvention;

FIG. 3 is a schematic view illustrating a mapping mode according to anembodiment of the present invention;

FIG. 4 is a schematic view illustrating another mapping mode accordingto an embodiment of the present invention;

FIG. 5 is a schematic view illustrating a mapping from LO ODU to HO OPU2according to an embodiment of the present invention;

FIG. 6 is a schematic view illustrating another mapping from LO ODU toHO OPU2 according to an embodiment of the present invention;

FIG. 7 is a schematic view illustrating another mapping from LO ODU toHO OPU2 according to an embodiment of the present invention;

FIG. 8 is a schematic view illustrating information encoding of“C8M-base+C8M-delta+C8-delta” according to an embodiment of the presentinvention;

FIG. 9 is a flowchart of a de-mapping method in an OTN according to anembodiment of the present invention;

FIG. 10 illustrates a mapping apparatus in an OTN according to anembodiment of the present invention;

FIG. 11 illustrates a mapping apparatus in an OTN according to anotherembodiment of the present invention; and

FIG. 12 illustrates a de-mapping apparatus in an OTN according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solutions of the embodiments of the present invention areclearly described as follows in conjunction with the drawings of theembodiments. It is apparent that the described embodiments are just apart of embodiments of the present invention, instead of all embodimentsthereof. Based on the embodiments of the present invention, otherembodiments, which are obtained by a person skilled in the art withoutpaying a creative effort, all fall within the protection scope of thepresent invention.

At the data transmitting side, as shown in FIG. 1 , a mapping method inan OTN according to an embodiment of the present invention includes:

constructing an ODTU according to an amount M of time slots of an HO OPUto be occupied by an LO ODU;

mapping the LO ODU to a payload area of the ODTU in an M-bytegranularity; encapsulating overhead information to the payload area ofthe ODTU; and

multiplexing the ODTU, which has been mapped the LO ODU and encapsulatedwith the overhead information, to the HO OPU, so as to provide anefficient and universal mode for mapping the LO ODU to the HO OPU.

For the convenience of understanding the embodiments of the presentinvention, the implementation processes of those embodiments duringspecific applications are described in detail as follows.

The mapping method in an OTN according to an embodiment of the presentinvention includes:

S1: constructing an ODTU according to an amount M of time slots of an HOOPU to be occupied by an LO ODU;

The step includes:

S11: determining the amount M of the time slots of the HO OPU to beoccupied by the LO ODU;

Specifically, the amount M of the time slots of the HO OPU to beoccupied by the LO ODU may be determined according to the rate of the LOODU and the rate of a single time slot of the HO OPU, i.e. M=upperrounding of (the rate of the LO ODU/the rate of a single time slot ofthe HO OPU). For example, HO OPU2 is divided into eight 1.25 G timeslots, and eight frames of HO OPU2 forms a large multi-frame, as shownin FIG. 2 . If the rate of a certain LO ODU is assumed as 6 G, then fivetime slots shall be occupied, and M is 5. We can allocate five timeslots to the current LO ODU according to the usage conditions of thetime slots in the HO OPU, herein the five time slots allocated to thecurrent LO ODU are assumed as time slots 2, 3, 5, 7 and 8.

Of course, other methods may also be adopted to determine M and allocatethe time slots to be occupied. Meanwhile, they are not limited by theembodiments of the present invention, and fall within the protectionscope of the embodiments of the present invention.

S12: constructing the ODTU;

The ODTU includes M time slots, and further includes JustificationControl Overhead (JC OH) corresponding to JC OH position of the HO OPU.As shown in FIG. 2 , the ODTU includes the time slots 2, 3, 5, 7 and 8in the multi-frame formed of eight HO OPUs, and further includes JC OHposition of HO OPU frames to which the respective time slots correspond.The shaded portions in FIG. 2 form corresponding ODTU.

S2: mapping the LO ODU to a payload area of the ODTU in an M-bytegranularity;

The step includes:

S21: determining an amount of LO ODU(s) of M-bytes to be mapped whenmapping in the M-byte granularity, according to an amount X of the LOODU(s) to be transmitted during each multi-frame period, and herein isrepresented as C8M; in another embodiment of the present invention,determining clock information according to the amount X of the LO ODU(s)to be transmitted during each multi-frame period, and herein isrepresented as C8-delta. The above two information is represented as“C8M+C8-delta”.

In which, the method for acquiring X is existing, and hence is notdescribed in the embodiments of the present invention.

Specifically, the embodiment of the present invention may use thefollowing method to determine “C8M+C8-delta”:C8M,MAX=(LO ODU rate*LO ODU maximum frequency deviation)/(M*TS rate*TSminimum frequency deviation)*15232C8M,MIN=(LO ODU rate*LO ODU minimum frequency deviation)/(M*TS rate*TSmaximum frequency deviation)*15232

Where C8M is an integer value with a range of [C8M, MIN lower rounding,C8M, MAX upper rounding]. C8-delta is X−M*C8M, indicating the clockinformation, where X is C8, and C8 is an integer value with a range of[C8, MIN lower rounding, C8, MAX upper rounding].C8,MAX=(LO ODU rate*LO ODU maximum frequency deviation)/(TS rate*TSminimum frequency deviation)*15232C8,MIN=(LO ODU rate*LO ODU minimum frequency deviation)/(TS rate*TSmaximum frequency deviation)*15232

Assuming a certain LO ODU has its X=76111 and occupies M=5 time slots,then C8M=(X/M) lower rounding=15222, C8-delta=X−M*C8M=1. Or C8M=(X/M)lower rounding+1=15223, C8-delta=X−M*C8M=−4. The mapped data informationand clock information can be completely reflected by transmitting theinformation “C8M+C8-delta”, i.e. (15222, 1) or (15223, −4). Thereceiving side may perceive, according to (15222, 1) or (15223, −4),that the transmitting side needs to transmit client data of 76111 bytesduring one multi-frame period, so as to accurately recover the clientclock at the receiving side.

The present invention may also use other methods to determine“C8M+C8-delta”. Meanwhile, they are not limited by the embodiments ofthe present invention, and all fall within the protection scope of thoseembodiments.

S22: mapping the amount of the LO ODU(s) of M-byte to the payload areaof the ODTU in the M-byte granularity.

Mapping in the M-byte granularity means performing one time of mappingoperation of M bytes of client data as a whole; as the above example,mapping the amount of the LO ODU(s) of M-byte to the payload area of theODTU in the M-byte granularity means mapping 15222 or 15223 LO ODUs of5-byte to the payload area of the ODTU, performing the mapping operationevery 5 bytes of LO ODU, and totally mapping for 15,222 or 15,223 times.

Specifically, the sigma-delta algorithm or other Generic MappingProcedure (GMP) mapping methods may be used to map the LO ODU(s) to thepayload area of the ODTU, the other GMP mapping methods meet thefollowing characteristics:

-   -   1. being capable of automatically determining a filling amount        according to the mapped signals and the rate of a target        container;    -   2. being capable of automatically determining distribution        positions of the filling and mapping signals in the target        container according to the mapped signals and the rate of the        target container; and    -   3. transporting position information carrying the filling and        mapping signals in the overhead of the target container.

The characteristic information of the GMP mapping method in theembodiments of the present invention is further described with thefollowing two mapping modes, but is not limited by the two mappingmodes.

Mapping mode 1: evenly distributing filling data and mapping signal datato the payload area through the sigma-delta algorithm. Information suchas positions of the filling and mapping signals is carried andtransported by the overhead of the target container; the effect afterthe mapping is shown in FIG. 3 , where S is filling data and D ismapping signal data; the filling data and the mapping signal data areevenly distributed to the payload area.

Mapping mode 2: concentratedly placing the filling data in a fixedposition of the payload area, and determining which portions in thepayload area are for the filling data and which portions in the payloadarea are for the mapping signal data according to the filling amount.Information such as positions of the filling and mapping signals iscarried and transported by the overhead of the target container; theeffect after the mapping is shown in FIG. 4 , where S is the fillingdata and D is the mapping signal data.

S3: encapsulating overhead information to the payload area of the ODTU;

In an embodiment of the present invention, the overhead informationincludes the amount information of the LO ODU(s) of M-byte, andencapsulating the overhead information to the payload area of the ODTUincludes:

encapsulating the amount information of the LO ODU(s) of M-byte to theoverhead area of the ODTU;

Specifically, encapsulating the amount information of the LO ODU(s) ofM-byte to the overhead area of the ODTU includes:

directly encapsulating the amount information of the LO ODU(s) of M-byteto the overhead area of the ODTU, and a form of “C8M” may be used; or

dividing the amount information of the LO ODU(s) of M-byte into a fixedportion of the amount information of the LO ODU(s) of M-byte and avariable portion of the amount information of the LO ODU(s) of M-byte,and encapsulating the fixed portion of the amount information of the LOODU(s) of M-byte and the variable portion of the amount information ofthe LO ODU(s) of M-byte to the overhead area of the ODTU; transportingin a form of this overhead information may also achieve the same effect.Specifically, a form of “C8M-base+C8M-delta” may be adopted, whereC8M-base+C8M-delta equivalent to C8M, indicating an amount of M-bytes inthe LO ODU(s) mapped to the payload area of the ODTU; C8M-base is anamount of M-bytes in the fixed portion, and C8M-delta is an amount ofM-bytes in the variable portion; or

determining amount information of the LO ODU(s) of M-byte to be filledaccording to the amount information of the LO ODU(s) of M-byte, andencapsulating the amount information of the LO ODU(s) of M-byte to befilled to the overhead area of the ODTU; Transmitting in a form of thisoverhead information may also achieve the same effect; specifically, aform of “S8M” may be adopted, where S represents the filling data, S8Mindicates an amount of filled bytes in the ODTU after the LO ODU(s) aremapped to the ODTU, and S8M=15232−C8M.

In another embodiment of the invention, the overhead informationincludes the amount information of the LO ODU(s) of M-byte and the clockinformation,

encapsulating the overhead information to the payload area of the ODTUincludes:

encapsulating the amount information of the LO ODU(s) of M-byte and theclock information to the overhead area of the ODTU.

Specifically, encapsulating the amount information of the LO ODU(s) ofM-byte and the clock information to the overhead area of the ODTUincludes:

directly encapsulating the amount information of the LO ODU(s) of M-byteand the clock information to the overhead area of the ODTU, and a formof “C8M+C8-delta” may be used; or

dividing the amount information of the LO ODU(s) of M-byte into a fixedportion of the amount information of the LO ODU(s) of M-byte and avariable portion of the amount information of the LO ODU(s) of M-byte,and encapsulating the fixed portion of the amount information of the LOODU(s) of M-byte and the variable portion of the amount information ofthe LO ODU(s) of M-byte to the overhead area of the ODTU; transportingin a form of this overhead information may also achieve the same effect;specifically, a form of “C8M-base+C8M-delta+C8-delta” may be used, whereC8M-base+C8M-delta equivalents to C8M, indicating an amount of M-bytesin the LO ODU(s) mapped to the payload area of the ODTU; C8M-base is anamount of M-bytes in the fixed portion, and C8M-delta is an amount ofM-bytes in the variable portion; or

determining amount information of the LO ODU(s) of M-byte to be filledaccording to the amount information of the LO ODU(s) of M-byte, andencapsulating the amount information of the LO ODU(s) of M-byte to befilled to the overhead area of the ODTU; transporting in a form of thisoverhead information may also achieve the same effect; specifically, aform of “S8M+S8-delta” may be adopted, where S represents the fillingdata, S8M indicates an amount of filled bytes in the ODTU after the LOODU(s) are mapped to the ODTU, S8M=15232−C8M, and S8-delta indicates theclock information.

Encapsulating the overhead information to the overhead area of the ODTUincludes:

encapsulating the overhead information to an overhead corresponding to afirst time slot or a last time slot in the ODTU.

The overhead information indicates clock information and an amount ofthe LO ODU(s) of M-byte mapped to the ODTU in next n multi-frames, orindicates clock information and an amount of the LO ODU(s) of M-bytemapped to the ODTU in next n frames, where n is a natural number.

In an embodiment of the present invention, the “C8M+C8-delta”information indicates conditions of the clock information and an amountof M-bytes in the LO ODU(s) mapped to the ODTU in the next multi-frame.

If the “C8M+C8-delta” information is encapsulated to the JC OHcorresponding to the first time slot in the ODTU, i.e. the JC OHposition of the 2^(nd) frame of HO OPU corresponding to the time slot 2in the current multi-frame, then the mapping process is shown in FIG. 5. If the “C8M+C8-delta” information is encapsulated to the JC OHcorresponding to the last time slot in the ODTU, i.e. the JC OH positionof the 8^(th) frame of HO OPU corresponding to the time slot 8 in thecurrent multi-frame, then the mapping process is shown in FIG. 6 .

In another one embodiment of the invention, the“C8M-base+C8M-delta+C8-delta” information indicates conditions of theclock information and an amount of M-bytes in the LO ODU(s) mapped tothe ODTU in the next frame of HO OPU.

Also taking HO OPU2 as an example, in the embodiment, as shown in FIG. 7, encapsulating “C8M-base+C8M-delta+C8-delta” to the JC OH positions ofthe 2^(nd), 3^(rd), 5^(th), 7^(th) and 8^(th) frames of HO OPU2corresponding to time slots 2, 3, 5, 7 and 8 in the current multi-frame,respectively. The information “C8M-base+C8M-delta+C8-delta” at the2^(nd), 3^(rd), 5^(th), 7^(th) and 8^(th) frames of HO OPU2 indicateclock information and amounts of M-bytes in the LO ODU(s) mapped to thepayload area of the ODTU in the next frame of HO OPU2, respectively. Theamount of M-bytes in the LO ODU(s) mapped to the payload area of theODTU in other frames of HO OPU2 is C8M-base; i.e. indicating mappingC8M-base+C8M-delta M-byte data of the LO ODU(s) in an M-byte granularityto the ODTU payload areas in the 3^(rd), 4^(th), 6^(th) and 8^(th)frames of HO OPUs in the current multi-frame and the ODTU payload areain the 1^(st) frame of HO OPU in the next multi-frame. Mapping C8M-baseM-byte data of the LO ODU(s) in an M-byte granularity to the ODTUpayload areas in the 2^(nd), 5^(th) and 7^(th) frames of HO OPUs.

In the embodiment of the present invention, the information“C8M-base+C8M-delta+C8-delta” may be encapsulated in the following mode,but not limited thereby, as shown in FIG. 8 .

In which, C8M-base occupies 13 bits, C8M-delta occupies 3 bits, C8-deltaoccupies 8 bits, and FEC occupies 8 bits; herein the FEC errorcorrecting function is added, and an encoding mode of BCH (16, 12) maybe used to achieve an effect of correcting an error of 1 bit, andimprove the reliability of the information “C8M-base+C8M-delta+C8-delta”during transportation. In addition, the FEC may also be replaced by CRC,and the information “C8M-base+C8M-delta+C8-delta” received at thereceiving side is ensured as correct through a CRC verification.

S4: multiplexing the ODTU, which has been mapped the LO ODU andencapsulated with the overhead information, to the HO OPU.

The mapping method in an OTN according to the embodiment of the presentinvention not only provides a high-efficient and universal mode formapping the LO ODU to the HO OPU, compatible with processes of mappingLO ODU to HO OPU in different granularities for the convenience ofinterconnection, but also separates the data information from the clockinformation to mapping in a large granularity, and carries the clockinformation with the byte granularity to solve the problem of poorperformance of clock recovered at the receiving side caused by mappingonly with large granularity.

Correspondingly, at the data receiving side, as shown in FIG. 9 , theembodiment of the present invention further provides a de-mapping methodin an OTN, for parsing an HO OPU to determine an ODTU and an amount M oftime slots occupied by the ODTU; and de-mapping an LO ODU from a payloadarea of the ODTU in an M-byte granularity.

De-mapping the LO ODU from the payload area of the ODTU in the M-bytegranularity includes:

acquiring information of an amount of the LO ODU of M-byte from theoverhead of the ODTU; and

de-mapping the amount of the LO ODU of M-byte from the payload area ofthe ODTU in the M-byte granularity.

De-mapping the LO ODU of M-byte from the payload area of the ODTU in theM-byte granularity further includes:

acquiring clock information from the overhead of the ODTU, andrecovering the clock of client service according to the clockinformation.

As shown in FIG. 10 , the embodiment of the present invention furtherprovides a mapping apparatus in an OTN, including:

a constructing unit, configured to construct an ODTU according to anamount M of time slots of an HO OPU to be occupied by an LO ODU;

a mapping unit, configured to for map the LO ODU to a payload area ofthe ODTU in an M-byte granularity;

an encapsulating unit, configured to encapsulate overhead information tothe payload area of the ODTU; and

a multiplexing unit, configured to multiplex the ODTU, which has beenmapped the LO ODU and encapsulated with the overhead information, to theHO OPU.

As shown in FIG. 11 , another embodiment of the present inventionprovides a mapping apparatus in an OTN, including the constructing unit,the mapping unit, the encapsulating unit and the multiplexing unit asshown in FIG. 10 , where the mapping unit includes:

a determining module, configured to determine an amount of the LO ODU ofM-byte to be mapped when mapping in an M-byte granularity, according toan amount X of the LO ODU to be transmitted in each multi-frame period;

a mapping module, configured to map the amount of the LO ODU of M-byteto the payload area of the ODTU in the M-byte granularity; and

the encapsulating unit is configured to encapsulate the amountinformation of the LO ODU of M-byte to the overhead area of the ODTU.

In another embodiment of the present invention, the determining moduleis further adopted for determining clock information according to theamount X of the LO ODU to be transmitted during each multi-frame period;and

the encapsulating unit is further configured to encapsulate the clockinformation to the overhead area of the ODTU.

As shown in FIG. 12 , the embodiment of the present invention furtherprovides a de-mapping apparatus in an OTN, including:

a parsing unit, configured to parse an HO OPU to determine an ODTU andan amount M of time slots occupied by the ODTU; and

a de-mapping unit, configured to de-map an LO ODU from a payload area ofthe ODTU in an M-byte granularity.

The detailed contents about signal processing and executions among thecomponents of the above apparatuses are based on the same concept of themethod embodiments of the present invention, please refer to thedescriptions of the method embodiments of the present invention, andherein are not described.

The above descriptions are just some exemplary embodiments of thepresent invention, and the protection scope of the present invention isnot limited thereby. Any modification or substitution that can be easilyconceived by a person skilled in the art within the technical scopedisclosed by the present invention shall be covered by the protectionscope of the present invention. Therefore, the protection scope of thepresent invention shall be subject to that of the claims.

What is claimed is:
 1. A method for processing data in an opticaltransport network (OTN), the method comprising: mapping, by a processorof an apparatus for processing data, a lower order optical channel dataunit (LO ODU) signal into a payload area of an optical channel datatributary unit (ODTU) signal; encapsulating, by the processor, overheadinformation to an overhead area of the ODTU signal; and multiplexing, bythe processor, the ODTU signal into a higher order optical channelpayload unit (HO OPU), wherein the ODTU signal occupies M tributaryslots of the HO OPU, and M is an integer greater than
 1. 2. The methodaccording to claim 1, wherein the overhead information comprisesinformation indicating a quantity of M-byte data groups of the LO ODUsignal that are mapped during a multi-frame period.
 3. The methodaccording to claim 2, wherein the overhead information further comprisesclock information that is determined according to the quantity of M-bytedata groups.
 4. The method according to claim 1, wherein the overheadinformation is only presented in a tributary slot in the overhead areaassociated with a last tributary slot among tributary slots that areoccupied by the ODTU signal.
 5. An apparatus for processing data in anoptical transport network (OTN), the apparatus comprising: a processorand a computer-readable non-transitory medium having a plurality ofcomputer executable instructions stored thereon which are executed bythe processor, to cause the processor to: map a lower order opticalchannel data unit (LO ODU) signal into a payload area of an opticalchannel data tributary unit (ODTU) signal; encapsulate overheadinformation to an overhead area of the ODTU signal; and multiplex theODTU signal into a higher order optical channel payload unit (HO OPU),wherein the ODTU signal occupies M tributary slots of the HO OPU, and Mis an integer greater than
 1. 6. The apparatus according to claim 5,wherein the overhead information comprises information indicating aquantity of M-byte data groups of the LO ODU signal that are mappedduring a multi-frame period.
 7. The apparatus according to claim 6,wherein the overhead information further comprises clock informationthat is determined according to the quantity of M-byte data groups. 8.The apparatus according to claim 5, wherein the overhead information isonly presented in a tributary slot in the overhead area associated witha last tributary slot among tributary slots that are occupied by theODTU signal.
 9. An apparatus for processing data in an optical transportnetwork (OTN), the apparatus comprising: a processor and acomputer-readable non-transitory medium having a plurality ofcomputer-executable instructions stored thereon which are executed bythe processor, to cause the processor to: map a low order opticalchannel data unit (LO ODU) signal into a payload area of an opticalchannel data tributary unit (ODTU) signal; multiplex the ODTU signalinto a high order optical channel payload unit (HO OPU), wherein theODTU signal occupies M tributary slots of the HO OPU, and M is aninteger greater than 1, and wherein the ODTU signal carries overheadinformation in an overhead area of the ODTU signal; map the HO OPU intoa high order optical channel data unit (HO ODU); map the HO ODU into ahigh order optical channel transport unit (HO OTU) signal; and send theHO OTU signal.
 10. The apparatus according to claim 9, wherein mappingthe LO ODU signal into the payload area of the ODTU signal is performedunder control of a generic mapping procedure (GMP) mapping mechanism.11. The apparatus according to claim 9, wherein the overhead informationcomprises clock information.
 12. A non-transitory, computer readablemedium storing instructions for execution by a processor, wherein whenexecuted by the processor, the instructions cause the processor toprovide at least the following operations in an optical transportnetwork (OTN): mapping a lower order optical channel data unit (LO ODU)signal into a payload area of an optical channel data tributary unit(ODTU) signal; encapsulating overhead information to an overhead area ofthe ODTU signal; and multiplexing the ODTU signal into a higher orderoptical channel payload unit (HO OPU), wherein the ODTU signal occupiesM tributary slots of the HO OPU, and M is an integer greater than
 1. 13.The non-transitory, computer readable medium according to claim 12,wherein the overhead information comprises information indicating aquantity of M-byte data groups of the LO ODU signal that are mappedduring a multi-frame period.
 14. The non-transitory, computer readablemedium according to claim 13, wherein the overhead information furthercomprises clock information that is determined according to the quantityof M-byte data groups.
 15. The non-transitory, computer readable mediumaccording to claim 12, wherein the overhead information is onlypresented in a tributary slot in the overhead area associated with alast tributary slot among tributary slots that are occupied by the ODTUsignal.